<input type="email">

input:valid { border: solid 2px green; }
input:invalid { border: solid 2px red; }

External CSS

  1. https://tim-montmorency.com/timdoc/shared/styles/codepen.css
  2. https://tim-montmorency.com/timdoc/shared/styles/codepen-form.css

External JavaScript

This Pen doesn't use any external JavaScript resources.